Do 404 errors and 301 redirects really hurt your SEO rankings?

This statement from Gary Illyes debunks two particularly persistent SEO myths in the industry. Many professionals still fear that a high volume of 404 errors or 301 redirects could dilute their "crawl budget" or send negative signals to algorithms.

Why does fear of 404s persist among SEOs?

404 errors have long been perceived as a sign of negligence — a poorly maintained site, broken links, poor user experience. This perception is partly based on advice from Search Console itself, which reports 404s as "errors" that need fixing.

The problem? Google conflates technical problems with business problems. A 404 is "technically" correct when a page no longer exists. But Search Console classifies it as an error because it can indicate a problem with internal linking or outdated content.

And 301 redirects — why this distrust?

301 redirects carry another legend: the loss of PageRank. For years, Google left doubt about a potential "bleeding" of SEO juice at each redirect. Matt Cutts had mentioned a minimal loss, which was enough to fuel collective paranoia.

Today, Google claims that 301s no longer dilute PageRank. But distrust remains, particularly around redirect chains and their impact on crawl time.

What does "harmless" actually mean for Google?

Illyes isn't saying that 404s and 301s have no consequences — he's saying they're not penalizing from an algorithmic standpoint. Important distinction.

A 404 doesn't impact the ranking of other pages on your site. A 301 doesn't cause you to lose "juice." But beware: a catastrophic user experience (broken links everywhere, redirect loops) will have indirect effects — bounce rate, behavioral signals, reputation.

• 404s don't penalize the site as a whole; only the affected page disappears from the index.
• 301s preserve PageRank and transmit authority to the new URL.
• The choice between 404 and 301 should be guided by business logic, not fear of an SEO penalty.
• Indirect signals (UX, user behavior) remain decisive, even if the errors themselves are "harmless."

Is this statement consistent with real-world observations?

Yes and no. In substance, field experience confirms that a site with a few hundred 404s doesn't suffer a manual or algorithmic penalty. 301 redirects, even in large volumes (site migration, redesign), don't cause a sharp drop if they're properly mapped.

But — and this is where Google's statement lacks nuance — redirect chains (A→B→C→D) do slow crawl efficiency and can delay indexing of the final page. Google theoretically follows up to 5 hops, but in practice, beyond 2-3 redirects, you observe significant indexing delays. [To verify] depending on the crawl resources allocated to each site.

What nuances should be added to this claim?

Google says "harmless," but doesn't specify scale. A site with 100 pages and 10 404 errors? No problem. An e-commerce site with 50,000 pages and 15,000 404 errors from obsolete products never cleaned up? Then you have a crawl budget management issue.

Googlebot continues crawling these dead URLs, sometimes for weeks or months. That crawl time could have been allocated to active pages, new content, strategic material. Saying "this isn't harmful" obscures this reality: it's wasted resources.

In what cases does this rule not fully apply?

The "404 = harmless" rule only holds if the page never had SEO value or its organic traffic was negligible. If you let a page that ranks in the top 3 for a strategic query go into 404 without a redirect, you lose that ranking. Obvious? Not for everyone.

Another edge case: domain migrations. Google officially recommends maintaining 301s for at least one year. But in practice, some sites keep redirects indefinitely out of fear of losing incoming links. Let's be honest: nobody knows exactly how long Google "remembers" a 301 after it's removed.

What should you concretely do with 404 errors?

First step: distinguish legitimate 404s from problematic ones. A page deleted intentionally (end-of-life product, outdated article) can stay in 404 without issue. But if that page was receiving organic traffic or backlinks, a 301 to equivalent content is preferable.

Second reflex: audit your internal linking. If your 404s come from broken internal links, it's a signal of poor technical hygiene. Search Console lists these URLs for you — fix the links or redirect them properly.

Third point: clean your XML sitemap. Never leave URLs returning 404 in your sitemap. It's wasted Googlebot time and an ambiguous signal ("I'm declaring this page important but it doesn't exist").

How to manage 301 redirects intelligently?

Avoid redirect chains at all costs. If A redirects to B, and B redirects to C, update A to redirect directly to C. It's basic housekeeping, but often neglected after multiple successive redesigns.

For site migrations, map each old URL to the most relevant new URL — not to the homepage by default. A "lazy" redirect of 500 product URLs to the homepage is technically a 301, but it destroys user experience and dilutes the thematic relevance of backlinks.

Finally, monitor redirect performance through your server logs. If a 301 still receives thousands of hits per month after a year, it means external sites or bookmarks still point to it — keep it active as long as necessary.

What mistakes should you absolutely avoid?

Never delete 301s "to clean up" without checking their traffic and backlinks. I've seen sites lose 20% of organic traffic in a month after cleaning up redirects deemed "unnecessary" — but which were still receiving third-party links.

Another classic trap: redirecting a page to one that's thematically distant. Google follows the 301, but if the new page doesn't match the search intent of the old one, users bounce immediately — and Google measures that.

• Audit your 404s via Search Console and distinguish which ones need a 301 from those that can stay as errors.
• Fix all internal links pointing to 404s — don't waste crawl budget.
• Remove any 404 URLs from your XML sitemap.
• Eliminate redirect chains by pointing directly to the final URL.
• Map each 301 to a thematically coherent page, never to the homepage by default.
• Keep 301s active as long as they receive significant traffic or backlinks.
• Monitor redirect performance through server logs and Google Analytics.